1. Field of the Invention
The present invention relates to an integrated, insulated-gate, field-effect transistor control device comprising at least one power transistor whose conduction path is connected in series with the device to be controlled between the terminals of a power supply and a control circuit having at least one input connected to a source of input control signals, and having an output connected to the gate of the said power transistor thereby applying to it control signals at a higher voltage than that of the input control signals and of the power supply.
2. Description of the Prior Art
Numerous circuits for apparatus of small volume such as watches and pocket calculators are fed by batteries. The voltage is then limited to a few volts if one does not want to assign too much space to the batteries. For example, the display devices, the micro-motor of a watch or light emitting diodes of the display in a calculator require relatively large currents.
The power transistors used for controlling an external device at a high current, such as for example a stepping motor or an LED display, are usually controlled by a device generating relatively low-voltage control signals. These power transistors designed for low-voltage control occupy a large portion of the total surface of the integrated circuit, which is a major drawback so far as cost and production efficiency are concerned.
It has already been suggested (French patent application No. 2 332 646), in order to control n-type MOS transistors, to increase the control voltage by means of a control circuit comprising a storage capacitor. This circuit however requires a capacity whose value is much higher than the capacities of the gates of the transistors to be controlled so that, in practice, it is not suitable for being integrated. On the other hand, the increase in the voltage which can be obtained is limited.
Furthermore, voltage multipliers using Schottky diodes and external capacities (U.S. Pat. No. 3,818,484) are known in integrated control devices for liquid crystal display devices. These multipliers are conceived for providing the necessary supply of power to these display devices and their control circuits, which conditions the way in which they are produced and makes very important the power output obtained.